Cationic polymers for sludge dewatering

ABSTRACT

A method of dewatering sludge is disclosed. This method comprises adding to the sludge an effective amount for the purpose of a polymer comprising repeat unit moieties of the compound methacryloxyethyl trimethyl ammonium chloride, said polymer having an intrinsic viscosity of about 1.0 to about 4.5 dl/g.

FIELD OF THE INVENTION

The present invention pertains to the use of particular water solublecationic homopolymers of a specific intrinsic viscosity range for sludgedewatering.

The homopolymers are obtained from the polymerization of cationicmonomers, namely quaternization products of dimethylaminoethylmethacrylate, diethylaminoethyl acrylate, dimethylaminoethyl acrylateand N,N-dimethylaminopropyl methacrylamide.

BACKGROUND OF THE INVENTION

With the increasing concern over pollution problems, sludge dewateringhas become an essential part of wastewater treatment programs. No longercan untreated sludge simply be dumped into the nearest river, lagoon orvacant lot. With this environmental interest in mind, improved sludgeconcentrating and dewatering techniques have become an important task inthe water treatment industry.

Generally, sludge is given primary dewatering treatment before beingdischarged from any given process system. Primary dewatering is usuallyaccomplished using thickeners/clarifiers or settling ponds. Secondarydewatering, including vacuum filtration, centrifugation, belt filters,lagoons, etc., is then commonly employed to further increase the solidscontent and reduce the water content in the resulting sludge to 50 to90% liquid. This can cause sludge dewatering to be a slow process.

In sludge handling facilities, problems often encountered in thedewatering process include the formation of sludge cake with highmoisture content, poor cake release from dewatering equipment, highdisposal costs, slow dewatering and poor equipment efficiency.

Improved sludge dewatering can lead to increased savings, especiallywith respect to the costs associated with transportation of the sludgeto be disposed.

Water soluble polyelectrolytes, such as anionic and cationic polymers,are often added to the sludge to aid in the production of a drier cakeand in the reduction of wear and tear on dewatering equipment.

As detailed in the Betz Handbook of Industrial Water Conditioning, 8thEdition, 1980, Betz Laboratories, Inc., Trevose, Pa., pages 253-256,cationic polymers can increase the settling rate of bacterial floc.These polymers further improve capture of the dispersed floc and cellfragments. By concentrating solids more quickly, the volume of recycleflow can be minimized so that the oxygen content of the sludge is notdepleted. Further, the waste sludge is usually more concentrated andwill require less treatment for eventual dewatering.

One problem with these anionic and cationic polymers is that theiroperating parameters are limited. The addition of too much of thesedewatering agents can cause the solids to disperse and defeat the wholepurpose of dewatering.

With the foregoing in mind, the present inventors embarked upon acomprehensive study in an attempt to dewater sludge in a more efficientfashion.

Accordingly, it is an object of the present invention to dewater sludgemore efficiently.

SUMMARY OF THE INVENTION

The present invention pertains to the use of particular water solublecationic homopolymers of a specific intrinsic viscosity range for sludgedewatering.

The homopolymers are obtained from the polymerization of cationicmonomers, namely quaternization products of dimethylamino ethylmethacrylate, diethylaminoethyl acrylate, dimethylaminoethyl acrylateand N,N-dimethylaminopropyl methacrylamide.

PRIOR ART

The use of cationic polymers for wastewater treatment is known in theart. As cited in "Polyelectrolytes for Water and Wastewater Treatment"chapters 6 and 7 (W. L. K. Schwoyer, CRC Press, 1981), it is generallybelieved that in settling and flocculation, there is a relationshipbetween molecular weight and effectiveness, with the higher molecularweight polymers of a given type being the most effective.

U.S. Pat. No. 3,023,162 (Fordyce, et al.) describes a homo polymer ofdimethylaminoethyl methacrylate quaternized with ethylene oxide orpropylene oxide for dewatering. The precise structure of the resultingpolymers after reaction is not identified. Polyalkylene oxide is usuallyformed from this type of reaction and may be attached to the amine site.This differs from the present invention in that the quaternization isachieved by the use of alkylene halides.

U.S. Pat. Nos. 4,319,013 and 4,396,752 (Cabestany et al.) teach that acationic copolymer of acrylamide and quaternized dimethylaminoethylacrylate can be used for dewatering. The effective copolymer is inpowder form and has an intrinsic viscosity higher than 6 dl/g. Thepresent invention differs in that the polymer is a homopolymer insolution form having an intrinsic viscosity less than 6 dl/g. Incontrast to the Prior Art, this polymer shows an unexpected improvementin sludge dewatering.

U.S. Pat. No. 4,396,513 (Haldeman) discloses the use of a cationiccopolymer consisting essentially of acrylamide (10-20%)/N,N -dimethylaminoethyl methacrylate methyl chloride (90-80%) with amolecular weight about one million and an intrinsic viscosity of atleast 5 dl/g for biological sludge dewatering. This patent also statesthat the copolymer performs better than the 100% cationic homopolymer inthe test conducted.

U.S. Pat. No. 4,699,951 (Allenson et al.) discloses a combination of twocationic polymers with vastly different molecular weights for treatingwater contaminated with oily waste and dispersed solids. The applicationand method of treatment differ from the present invention in that it isa polymer admixture that is applied to the wastewater.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the invention, cationic homopolymers comprising thepolymerization products of ethylenically unsaturated cationic monomerssuch as quaternized dimethylaminoethyl methacrylate, diethylaminoethylacrylate, dimethylaminoethyl acrylate, N,N-dimethylaminopropylmethacrylamide, and N,N-dimethylaminopropyl acrylamide, etc. Thesecationic homopolymers are unexpectedly effective in sludge dewatering atan intrinsic viscosity range of 1.0 to 4.5 dl/g, preferably 1.5 to 4.0dl/g, more preferably 1.5 to 2.0 dl/g.

The cationic monomers are obtained from a quaternization reaction of theabove described monomers with alkyl or aryl halides such as methylchloride, methyl bromide, benzyl chloride, or dimethyl sulfate. Theresulting cationic monomer is then polymerized by conventionalpolymerization techniques. Any of the well known initiators such as azocompounds, peroxides, redox couples and persulfates may be used topolymerize the cationic monomers. Radiation, thermal or photochemicalpolymerization methods may also be used to yield the polymer. Likewise,for those skilled in the art, any method such as chain transfer agents,concentration, temperature and addition rate variations may be used toregulate the viscosity or molecular weight of the resulting polymer. Thepolymerization may be conducted in solution, suspension, bulk oremulsion. In the emulsion polymerization, a water-in-oil inverseemulsion technique as disclosed in U.S. Pat. Nos. 3,284,393, Re. 28,474and Re. 28,576 is preferred. The reaction will generally occur between20° and 100° C., pending the initiation system and polymerization mediumused. The pH of the reaction mixture is generally in the range of 2.0 to7.0. Higher pH will cause the hydrolysis of the cationic monomer.

The preferred method in accordance to the invention is to polymerize thecationic monomer in an aqueous medium using persulfate as an initiatorat 80° to 95° C. and at a pH of 2.0 to 4.0. The desired viscosity of thepolymer is regulated by adding a proper amount of persulfate, cationicmonomer and water during polymerization. The resulting polymer isverified by viscosity increase, light scattering measurement and carbon13 nuclear magnetic resonance (NMR) spectroscopy. Intrinsic viscosity ofthe polymer is measured in 1M sodium chloride solution at 30° C. TheHuggins equation is used to determine the intrinsic viscosity. Accordingto established theory and equations in the art, intrinsic viscosityvalues can be correlated with the molecular weight of the polymer. Ahigher intrinsic viscosity of the polymer will represent a highermolecular weight. This is illustrated in Billmeyer's "Textbook ofPolymer Science" pages 208 to 213 (1984). The specific homopolymer whichhas proven to be most effective as a dewatering aid comprises repeatunit moieties having the structure ##STR1## wherein R is H or methyl.

Intrinsic viscosity of the polymer in accordance with this invention isabout 1.0 to 4.5 dl/g, preferably 1.5 to 4.0 dl/g, more preferably 1.5to 2.0 dl/g.

The method of preparation of the homopolymer methacryloyloxyethyltrimethyl ammonium chloride (METAC) designated as Sample Number 1 inTable I is detailed below.

A suitable reaction flask was equipped with a mechanical agitator, athermometer, a condenser, a nitrogen inlet and addition inlets forreagents. The flask was charged with 40.0 g of 75% METAC and 20 g ofdeionized water. The resulting solution was heated to 90° C. under anitrogen blanket. An initiator solution containing 0.5% of sodiumpersulfate in deionized water was prepared separately and sparged withnitrogen. The initiator solution (7.5 g) was then added to the reactionflask over 270 minutes at 90° C. Three 20 g aliquots of deaerated,deionized water were added to the reaction at the 30, 90 and 210 minuteaddition intervals. The reaction was held at temperature for 60 minutesfollowed by the addition of 120 g of deionized water. After mixing at90° C. for another 30 minutes the reaction mixture was cooled to roomtemperature.

The homopolymer solution, after being diluted to 10.6% solids, had aBrookfield viscosity of 1160 cps. The resulting product was a clearsolution with a pH at 3.3. The structure of the polymer was verified byC 13 NMR. The structure was characterized by a broad polyacrylate typebackbone and no evidence of unreacted monomer. Intrinsic viscosity ofthe polymer was 1.5 dl/g as measured in 1M sodium chloride solution at30 C.

The polymer is added to the sludge to be treated in an amount of about80 to 600 ppm active, preferably 100 to 350 ppm active. These dosagescorrespond to about 5 to 40 pounds active polymer per ton of dry sludge,based on an average sludge solids of 3%. The polymer may be addeddirectly to the sludge after it has been clarified. The polymer may alsobe added after the sludge has been subjected to a thickener, digester orthe like. The polymer may also be added to the sludge prior to otherdewatering processes such as belt filters, vacuum filters, centrifugesor lagoons.

Compounds such as alum, ferric chloride, anionic polymers such ascopolymers of acrylamide with acrylic acid,2-acrylamido-2-methylpropylsulfonic acid or styrene sulfonate etc., andother cationic polymers for example, polydimethyldiallyl ammoniumchloride (DMDAC); condensation product of epichlorohydrin withalkylamines; copolymers of acrylamide with DMDAC, methacryloyloxyethyltrimethyl ammonium methosulfate (METAMS), methacrylamido propyltrimethylammonium chloride, (MAPTAC), acrylamido propyltrimethyl ammoniumchloride (APTAC), acryloyloxyethyl trimethyl ammonium chloride (AETAC),methacryloyloxyethyl trimethyl ammonium chloride (METAC), acryloyloxyethyl diethylmethyl ammonium chloride or their methyl sulfate quats maybe used in conjunction with the polymers in this invention for sludgedewatering.

BRIEF DESCRIPTION OF THE DRAWINGS

The appended drawings graphically present the data generated by theexamples which are reported hereinbelow. In the Drawings:

FIG. #1 is a graph showing the capillary suction time of variousconditioned samples tested in Table III.

FIG. #2 is a graph showing the capillary suction time of otherconditioned samples tested in Table III.

FIG. #3 is a graph showing the percent caked solids of conditionedsamples tested in Table IV and V.

FIG. #4 is a graph showing the percent solids captured of conditionedsamples tested in Tables IV and V.

FIG. #5 is a graph showing the percent caked solids of conditionedsamples tested in Table VI.

FIG. #6 is a graph showing the percent solids captured of conditionedsamples tested in Table VI.

FIG. #7 is a graph showing the percent cake solids of conditionedsamples tested in Table VI.

FIG. #8 is a graph showing the percent solids captured of conditionedsamples tested in Table VI.

FIG. #9 is a graph showing the percent cake solids of conditionedsamples tested in Table VII.

FIG. #10 is a graph showing the percent solids captured of conditionedsamples tested in Table VII.

EXAMPLES The following examples are illustrative only and should not beconstrued as limiting the invention. SAMPLES

Homopolymers of (meth)acryloyloxyethyl trimethyl ammonium chloride wereprepared in aqueous solution using sodium persulfate as an initiator at80° to 95° C. A proper amount of water was added during the reaction toregulate the desired viscosity (molecular weight) of the product. Noresidual monomer was detected by carbon 13 nuclear magnetic resonancemeasurement. Intrinsic viscosity of the polymer was measured in 1Msodium chloride solution at 30° C.

Table I below presents a summary of the physical properties of theresulting polymers produced by the above method.

                                      TABLE I                                     __________________________________________________________________________    Polymer Properties                                                                                Brookfield                                                                    Viscosity,                                                                             Intrinsic                                        Sample Number                                                                         Composition                                                                          % Solids                                                                           cps. at 25° C.                                                                pH                                                                              Viscosity, dl/g                                  __________________________________________________________________________    1 (1555-43)                                                                           METAC  10.6 1160   3.3                                                                             1.5                                              2 (1555-45)                                                                           AETAC  9.9  1444   2.9                                                                             1.7                                              3 (1577-32)                                                                           METAC  9.6  12040  3.2                                                                             2.9                                               4 (1485-281)                                                                         METAC  3.5   114   3.5                                                                              0.86                                            __________________________________________________________________________     METAC = methacryloyloxyethyl trimethyl ammonium chloride                      AETAC = acryloyloxyethyl trimethyl ammonium chloride                     

Comparative dewatering tests were also performed using the well-knownpolymers described in the prior art. These are described in Table II.

                  TABLE I                                                         ______________________________________                                        Comparative Polymers                                                                                     Intrinsic                                          Polymer                                                                              Description         Viscosity, dl/g                                    ______________________________________                                        A      Copolymer of acrylamide/metac                                                                     8.9                                                B      Polymetac           5.4                                                C      Polydimethyldiallyl Ammonium                                                                      1.4                                                       Chloride                                                               D      Polydimethyldiallyl Ammonium                                                                      0.8                                                       Chloride (DMDAC)                                                       E      Polydimethyldiallyl Ammonium                                                                      1.5                                                       Chloride (DMDAC)                                                       ______________________________________                                    

DEWATERING ACTIVITY TEST

The relative dewatering performance of the polymers was evaluated by twodifferent test methods, capillary suction time (CST) and a laboratorybelt filter press. Mixtures of primary and secondary sludge from apharmaceutical plant in New Jersey taken on four different dates wereused for evaluation.

In the CST test, an aliquot of sludge is placed in a cylindrical cellwhich is placed on top of a piece of chromatography paper. The capillarypressure exerted by the paper draws the water out of the sludge. A timerrecords the time in seconds required for the water to pass between twofixed points. Shorter times indicate better dewatering efficacy. Resultsare evaluated by preparing a graph of CST versus treatment dosage.Generally, the treatment which produces the lowest CST value at thelowest dosage is the most effective. The results appear in FIGS. 1 and 2and the data used to generate these figures is found in Table III.Letters A through E represent the comparative polymer results, whilenumbers 1 through 4 represent the homopolymers of the present invention.

A Larox laboratory scale belt filter press was the second methodemployed to evaluate polymer dewatering performance. The design of thisinstrument permits modeling of full-scale belt filter press operationsby adjustment of conditions such as solids loading, filter media, freedrainage time, pressure and press time. The sludge cake produced fromthe laboratory scale belt filter press is analyzed for percent solidsand percent solids capture, with solids capture being defined as thequantity of solids retained by the belt filter media compared to thequantity of solids loaded on the press. Results are evaluated byplotting percent solids and percent solids capture results versustreatment dosage. Higher values of percent sludge cake solids andpercent solids capture indicates a higher degree of dewatering andbetter treatment performance. Dosages for conducting evaluations on thelaboratory belt filter press were selected based on the results of theCST tests. Sludge characteristics and test conditions are described inthe Tables below. The results have been plotted and appear in FIGS. 3 to10. Data used to generate the graphs is presented in Tables IV to VII.Letters A through E represent the comparative polymer results, whilenumbers 1 through 4 represent the homopolymers of the present invention.

    ______________________________________                                        Test Conditions                                                               ______________________________________                                        Substrate Volume:                                                                          200 mL                                                           Substrate Solids:                                                                          2.85%                                                            Substrate pH:                                                                              6.90                                                             Treatment mixing:                                                                          5 seconds @ 550 RPM prior to treatment                                        addition                                                                      30 seconds @ 550 RPM after treatment                                          addition                                                         ______________________________________                                    

                  TABLE III                                                       ______________________________________                                        Capillary Suction Time (Seconds):                                             Polymer                                                                       Dosage                                                                        Treatment:                                                                    (ppm, active)                                                                          A      B      C    #3    #1    D     #2                              ______________________________________                                         25                         246.7 144.5                                        50                         143.5 60.6  304.35                                                                              114.7                            65                                     13.7                                   75                    93.2 54.3  10.8  175.90                                                                               26.0                           100      84.2   64.5   52.9 22.2  6.4   44.60  13.7                           115                         10.2                                              120             62.2                                                          125      54.3   30.4   28.6  9.5  6.8                                         135      22.7    7.0   23.3                                                   150       8.2    8.0    7.3  6.9  8.0                                         175       7.9   12.8   13.4  7.3                                              200      18.4   19.6                    23.70  11.5                           225      25.7   29.2                                                          250                                     15.90  8.1                            300                                     10.30  8.3                            350                                            8.4                            400                                      8.50  8.0                            500                                            8.4                            600                                     10.55                                 700                                            9.5                            800                                     16.90  11.6                           ______________________________________                                    

    ______________________________________                                        Substrate Solids:                                                                         2.79%                                                             Substrate pH:                                                                             6.53                                                              Loading Rate:                                                                             2.188 × 10E-02 grams/cm.sup.2                               Cycle:      20 seconds of Free Drainage                                                   40 seconds @ 40 psig                                              Belt Cloth: Parkson P-28S (smooth side used for contact                                   with sludge)                                                      Blank       no cake formed                                                    Treatment mixing:                                                                         5 seconds @ 550 RPM prior to treatment                                        addition                                                                      30 seconds @ 550 RPM after treatment                                          addition.                                                         ______________________________________                                    

                  TABLE IV                                                        ______________________________________                                        Laboratory Scale Belt Filter Press Tests                                              Polymer Dosage                                                                              Percent   Percent                                       Treatment                                                                             (ppm, active) Cake Solids                                                                             Solids Capture                                ______________________________________                                        A       100           4.85      13.94                                                 150           5.19      21.00                                                 200           7.02      36.36                                                 250           8.30      55.00                                                 350           7.99      53.00                                         D        50           5.04       7.31                                                 100           5.23      11.63                                                 300           8.15      39.86                                                 450           8.77      46.09                                                 600           7.96      44.80                                         B       100           4.95      16.47                                                 150           7.15      24.00                                                 200           8.48      39.00                                                 250           9.75      53.50                                                 350           10.21     60.80                                         C       100           5.49      13.85                                                 125           5.57      18.60                                                 150           5.95      21.50                                                 200           7.06      30.59                                                 300           7.58      41.90                                         #3       75           5.20      13.28                                                 125           6.25      20.25                                                 150           7.11      27.99                                                 200           9.31      55.35                                                 300           10.15     70.34                                         #1       50           5.82      17.91                                                  75           6.90      32.40                                                 100           8.60      46.36                                                 150           9.58      57.63                                                 200           9.32      54.16                                         #2      100           5.73      14.91                                                 150           6.15      21.20                                                 250           8.01      30.60                                                 350           8.56      43.40                                                 500           9.49      54.66                                         ______________________________________                                    

    ______________________________________                                        Substrate Solids:                                                                         2.71%                                                             Substrate pH;                                                                             6.85                                                              Loading Rate:                                                                             2.188 × 10-02 grams/cm.sup.2                                Cycle:      20 seconds of free drainage                                                   40 seconds @ 100 psig                                             Blank       no cake formed                                                    Treatment mixing:                                                                         5 seconds @ 550 RPM prior to treatment                                        addition                                                                      30 seconds @ 550 RPM after treatment                                          addition.                                                         ______________________________________                                    

                  TABLE V                                                         ______________________________________                                        Laboratory Scale Belt Filter Press Tests                                              Polymer Dosage                                                                              Percent   Percent                                       Treatment                                                                             (ppm, active) Cake Solids                                                                             Solids Capture                                ______________________________________                                        C       100           5.671     28.98                                                 150           6.893     34.24                                                 185           7.712     42.63                                                 200           8.164     45.68                                                 250           8.824     52.64                                                 300           10.851    66.05                                         #4      100           6.757     30.69                                                 150           6.950     34.20                                                 185           7.311     40.01                                                 200           7.510     45.20                                                 250           7.965     47.90                                                 300           8.850     51.15                                         #1      100           6.367     34.94                                                 150           8.038     49.94                                                 185           9.491     58.57                                                 200           9.702     63.82                                                 250           10.490    68.71                                                 300           11.168    72.49                                         B       100           6.548     32.41                                                 150           8.707     55.99                                                 185           9.860     67.30                                                 200           10.900    75.72                                                 250           11.850    82.10                                                 300           12.030    82.03                                         ______________________________________                                    

    ______________________________________                                        Substrate Solids:                                                                         2.71%                                                             Substrate pH;                                                                             6.85                                                              Loading Rate:                                                                             2.188 × 10E-02 grams/cm.sup.2                               Cycle:      20 seconds of free drainage                                                   40 seconds @ 90 psig                                              Blank       no cake formed                                                    Treatment mixing:                                                                         5 seconds @ 550 RPM prior to treatment                                        addition                                                                      30 seconds @ 550 RPM after treatment                                          addition                                                          ______________________________________                                    

                  TABLE VI                                                        ______________________________________                                        Laboratory Scale Belt Filter Press Tests                                              Polymer Dosage                                                                              Percent   Percent                                       Treatment                                                                             (ppm, active) Cake Solids                                                                             Solids Capture                                ______________________________________                                        D        50           5.179     14.39                                                 100           5.867     27.14                                                 200           7.844     45.12                                                 450           11.840    75.89                                         C        50           4.769     15.29                                                 100           6.519     25.69                                                 200           9.250     53.34                                                 450           12.160    79.99                                         E        50           5.382     16.88                                                 100           6.280     31.86                                                 200           8.450     49.96                                                 450           12.560    86.68                                         #1       50           5.356     20.58                                                 100           7.629     40.56                                                 200           10.684    72.64                                                 450           12.960    97.75                                         #2       50           4.853     16.10                                                 100           7.130     35.69                                                 200           9.450     57.23                                                 450           14.060    95.59                                         ______________________________________                                    

    ______________________________________                                        Substrate Solids:                                                                         2.71%                                                             Substrate pH;                                                                             6.85                                                              Loading Rate:                                                                             2.188 × 10E-02 grams/cm.sup.2                               Cycle:      20 seconds of free drainage                                                   40 seconds @ 100 psig                                             Blank       no cake formed                                                    Treatment mixing:                                                                         5 seconds @ 550 RPM prior to treatment                                        addition                                                                      30 seconds @ 550 RPM after treatment                                          addition                                                          ______________________________________                                    

                  TABLE VII                                                       ______________________________________                                        Laboratory Scale Belt Filter Press Tests                                              Polymer Dosage                                                                              Percent   Percent                                       Treatment                                                                             (ppm, active) Cake Solids                                                                             Solids Capture                                ______________________________________                                        D       100           5.883     19.83                                                 150           6.822     32.85                                                 185           7.610     36.25                                                 200           7.953     38.02                                                 250           8.120     38.35                                         C       100           5.915     24.20                                                 150           7.138     36.58                                                 185           7.575     43.90                                                 200           8.180     47.80                                                 250           9.386     54.34                                         E       100           6.257     26.28                                                 150           7.280     38.50                                                 185           8.312     48.26                                                 200           8.601     52.79                                                 250           9.687     62.23                                         #1      100           6.889     40.71                                                 150           8.673     47.55                                                 185           10.253    60.03                                                 200           10.856    66.35                                                 250           11.675    75.50                                         #2      100           6.013     29.39                                                 150           7.867     43.28                                                 185           9.389     52.56                                                 200           10.106    54.95                                                 250           11.762    67.45                                         ______________________________________                                    

The examples demonstrate that the polymers in this invention exhibitsurprisingly superior performance when compared to the conventional orwell known polymers as described in the prior art. The polymersaccording to the invention promote higher cake solids in the sludgedewatering tests which have both environmental and economical benefits.They also have a wider effective dosage range as compared to the priorart polymers making it easier to control the polymer dosage in atreatment plant.

In accordance with the patent statutes, the best mode of practicing theinvention has been herein set forth. However, it will be apparent tothose skilled in the art that many modifications can be made in themethods herein disclosed without departing from the spirit of theinvention.

What is claimed is:
 1. Method of dewatering aqueous sludge, wherein saidsludge is a mixture of primary and secondary sludge from apharmaceutical plant, comprising adding to said sludge an effectiveamount for the purpose a homopolymer, said homopolymer comprising repeatunit moieties having the structure: ##STR2## wherein R is H or methyland having an intrinsic viscosity from about 1.0 to about 2.9 dl/g asmeasured in 1M sodium chloride at 30° C.
 2. Method as defined in claim 1wherein said homopolymer has an intrinsic viscosity from about 1.5 toabout 2.0 dl/g.
 3. Method as defined in claim 1 wherein R is H. 4.Method as defined in claim 1 wherein R is methyl.
 5. Method as definedin claim 1 comprising adding said homopolymer to said sludge in theamount of about 5 to about 40 pounds active polymer per ton of drysludge.
 6. Method as defined in claim 1 wherein said dewatering aqueoussludge further comprises dewatering said sludge in a belt filtermechanism.
 7. Method as defined in claim 1 wherein said dewateringaqueous sludge further comprises dewatering said sludge in a vacuumfilter mechanism.
 8. Method as defined in claim 1 wherein saiddewatering aqueous sludge further comprises dewatering said sludge in acentrifuge.
 9. Method as defined in claim 1 wherein said dewateringaqueous sludge further comprises dewatering said sludge in a lagoon. 10.Method as defined in claim 1 wherein said dewatering aqueous sludgefurther comprises dewatering said sludge in a waste water treatmentsystem.